The wireless local-area network (WLAN) technology known as “Wi-Fi” has been standardized by IEEE in the 802.11 series of specifications (i.e., as “IEEE Standard for Information technology—Telecommunications and information exchange between systems. Local and metropolitan area networks—Specific requirements. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”).
Cellular operators that are currently serving mobile users with, for example, any of the technologies standardized by the 3rd-Generation Partnership Project (3GPP), including the radio-access technologies known as Long-Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS)/Wideband Code-Division Multiple Access (WCDMA), High Speed Packet Access (HSPA) and Global System for Mobile Communications (GSM), see Wi-Fi as a wireless technology that can provide good additional support for users in their regular cellular networks. There is interest around using the Wi-Fi technology as an extension, or alternative to cellular radio access network technologies to handle the always increasing wireless bandwidth demands. The term “operator-controlled Wi-Fi” points to a Wi-Fi deployment that on some level is integrated with a cellular network operator's existing network and where the 3GPP radio access networks and the Wi-Fi wireless access may even be connected to the same core network and provide the same services.
3GPP is currently working on specifying a feature/mechanism for WLAN/3GPP Radio interworking which improves operator control with respect to how a UE performs access selection and traffic steering between 3GPP and WLANs belonging to the operator or its partners. Three different solutions have been described in 3GPP TR 37.834 v12.0.0 (2013-December) “Study on Wireless Local Area Network (WLAN)—3GPP radio interworking (Release 12)”.
In one of the solutions (Solution 2 in TR 37.834), which is also referred to as the “threshold-based mechanism” herein, the 3GPP network (i.e. network node of the first RAT) provides to the UE (the term used to refer to a terminal device by 3GPP) conditions and/or thresholds which are used by the UE in one or more pre-defined rules dictating when the terminal device should steer traffic from one RAT to the other.
In another one of the solutions (Solution 3 in TR 37.834), which is also referred to a “traffic steering command based mechanism” herein, the (3GPP) network configures the UE to send measurement reports related to WLANs the terminal device has discovered (or to WLANs for which certain conditions have been fulfilled). The network would, based on these measurement reports, decide whether the terminal device shall steer traffic towards the reported WLANs. If a terminal device is to steer traffic towards a WLAN, the network sends a traffic steering command to that terminal device.
In both of the above solutions, identifiers of WLANs (also referred to as WLAN identifiers) may need to be communicated between the radio access network, RAN, and the UE. In the threshold-based mechanism, the RAN may communicate a list of WLAN identifiers to the UE that are acceptable for the UE to consider when evaluating the pre-defined rules. In the traffic steering command based mechanism, the RAN may communicate a list of WLAN identifiers to the UE that the UE is to measure, and the UE may communicate the identity of one or more WLANs (i.e. the WLAN identifiers) that fulfill the conditions to the RAN.
WLAN identifiers are large, for example, a Service Set Indicator (SSID) may be up to 32 bytes. The communication of the WLAN identifiers between the RAN and UE (and between nodes in the network in the event that the WLAN identifier list is provided from one node to another) can therefore generate a lot of signaling between the network and the UE just to identify WLANs. This signaling will decrease system capacity, increase terminal device power consumption, generate interference, etc.
A similar problem exists for other types of WLAN identifiers, such basic SSIDs, BSSIDs, extended SSIDs, ESSIDs, homogenous ESSIDs, HESSIDs, Realm identifiers, Network Access Indicators, NAIs, public land mobile network, PLMN, identifiers, or Domain Name lists, as well as identifiers for networks operating according to other radio access technologies (RATs).
It will be appreciated that these problems are not confined to the communication of network identifiers as part of an interworking mechanism, and that they can arise in other situations where one or more network identifiers are communicated between a UE and network node (or between network nodes).
Therefore, there is a need for a technique for the efficient communication of network identifiers, for example identifiers of WLANs, between a terminal device and a network node, or between network nodes.